I had no idea, thank you.

This is often called "sterile transit" (the ability to depart the airport without passing through immigration), and the U.S. and Mexico (and apparently Canada) don't allow this, while generally European and Asian countries do.

https://wikitravel.org/en/Avoiding_a_transit_of_the_United_S...

No EU airport allows this for flights from outside the EU/Schengen zone. Every international airport has dedicated "EU internal" and "all other" terminal pathways for this reason.

Yes, they do. Unless I misinterpreted your comment, connection flights from outside EU to US/Canada don’t require the Schengen visa as passengers don’t leave the “clean” zone.

I've had to go through security and immigration when flying through Dublin and Seoul. So I don't think you can exempt Europe and Asia from the list.

Were you flying to or from somewhere else in Europe in the Dublin case? A subtlety about this which has just come up elsewhere in this thread is that the whole Schengen Area is treated as a single "country" for immigration purposes, so if you have an intra-European flight, you have to enter or exit "Europe" in the course of a transfer to or from an external flight.

But I think if you fly, for example, from New York to Paris and then on to Tunis, you don't have to go through immigration controls in Paris.

I was flying from Seattle to Rome with a connecting flight in Dublin. In both Rome and Dublin I had to go through immigration (that is, present my passport) and in Dublin I had my carry on X-rayed again. Upon arrival in Rome, after clearing immigration I had to go through customs, which is to say I walked out the "Nothing to Declare" portal.

Oh, I just remembered that Ireland isn't in the Schengen Area (due to the Common Travel Area with the UK). So you wouldn't have a domestic-style flight from Ireland to Italy. But your experience then does seem to confirm that Dublin doesn't offer sterile transit at all, which is a bit of a surprise to me.